The objective of this core is to develop, breed and provide new transgenic mouse strains to be used for in vivo studies in the laboratory programs. The core will provide transgenic mice expression TIMP-1, ecotin and/or cystatins under constitutive and regulated promoters bred onto FVB/N and immunocompromised backgrounds, and humanized transgenic mice expressing human metalloproteinases under control of endogenous human promoters. The core will breed specific metalloprotease or inhibitor null-mutant mice onto backgrounds suitable for use in studies with isogenic and xenogenic cancer models. These models will lead to assessment of the pathogenesis and potential antiprotease therapy with greater specificity than animal models currently available.